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Modulation of the vertical particle transfer efficiency in the oxygen minimum zone off Peru

Abstract.

"The fate of the organic matter (OM) produced by marine life controls the major biogeochemical cycles of the Earth's system. The OM produced through photosynthesis is either preserved, exported towards sediments or degraded through remineralisation in the water column. The productive eastern boundary upwelling systems (EBUSs) associated with oxygen minimum zones (OMZs) would be expected to foster OM preservation due to low O2 conditions. But their intense and diverse microbial activity should enhance OM degradation. To investigate this contradiction, sediment traps were deployed near the oxycline and in the OMZ core on an instrumented moored line off Peru. [...]"

Source: Biogeosciences
Authors: Marine Bretagnon et al.
DOI: 10.5194/bg-15-5093-2018

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H2S events in the Peruvian oxygen minimum zone facilitate enhanced dissolved Fe concentrations

Abstract.

"Dissolved iron (DFe) concentrations in oxygen minimum zones (OMZs) of Eastern Boundary Upwelling Systems are enhanced as a result of high supply rates from anoxic sediments. However, pronounced variations in DFe concentrations in anoxic coastal waters of the Peruvian OMZ indicate that there are factors in addition to dissolved oxygen concentrations (O2) that control Fe cycling. [...]"

Source: Scientific Reports
Authors: Christian Schlosser et al. 
DOI: 10.1038/s41598-018-30580-w

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The devil's in the disequilibrium: multi-component analysis of dissolved carbon and oxygen changes under a broad range of forcings...

...in a general circulation model

Abstract.

"The complexity of dissolved gas cycling in the ocean presents a challenge for mechanistic understanding and can hinder model intercomparison. One helpful approach is the conceptualization of dissolved gases as the sum of multiple, strictly defined components. Here we decompose dissolved inorganic carbon (DIC) into four components: saturation (DICsat), disequilibrium (DICdis), carbonate (DICcarb), and soft tissue (DICsoft). The cycling of dissolved oxygen is simpler, but can still be aided by considering O2, O2sat, and O2dis. [...]"

Source: Biogeosciences
Authors: Sarah Eggleston and Eric D. Galbraith
DOI: 10.5194/bg-15-3761-2018

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Ventilation of oxygen to oxygen minimum zone due to anticyclonic eddies in the Bay of Bengal

Abstract.

"Intense oxygen minimum zone (OMZ) occurs in the mid‐depth of the Eastern Tropical Pacific (ETP), Arabian Sea (AS), and Bay of Bengal (BoB). However, the occurrence of anammox/denitrification was reported only in the ETP and AS and its absence in the BoB is attributed to presence of traces of dissolved oxygen (DO). Anticyclonic Eddies (ACE) supply high nutrient, organic‐rich and oxygen poor waters from the coastal upwelling regions leading to strengthening of OMZ in the offshore of AS and ETP.  [...]"

Source: Biogeosciences
Authors: V. V. S. S. Sarma, T. V. S. Udaya Bhaskar
DOI: 10.1029/2018JG004447

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Reversal of Increasing Tropical Ocean Hypoxia Trends With Sustained Climate Warming

Abstract.

"Dissolved oxygen (O2) is essential for the survival of marine animals. Climate change impacts on future oxygen distributions could modify species biogeography, trophic interactions, biodiversity, and biogeochemistry. The Coupled Model Intercomparison Project Phase 5 models predict a decreasing trend in marine O2 over the 21st century.  [...]"

Source: Global Biogeochemical Cycles
Authors: Weiwei Fu et al.
DOI: 10.1002/2017GB005788

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A Sixteen-year Decline in Dissolved Oxygen in the Central California Current

Abstract.

"A potential consequence of climate change is global decrease in dissolved oxygen at depth in the oceans due to changes in the balance of ventilation, mixing, respiration, and photosynthesis. We present hydrographic cruise observations of declining dissolved oxygen collected along CalCOFI Line 66.7 (Line 67) off of Monterey Bay, in the Central California Current region, and investigate likely mechanisms.  [...]"

Source: Scientific Reports
Authors: Alice S. Ren et al.
DOI: 10.1038/s41598-018-25341-8

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The competing impacts of climate change and nutrient reductions on dissolved oxygen in Chesapeake Bay

Abstract.

"The Chesapeake Bay region is projected to experience changes in temperature, sea level, and precipitation as a result of climate change. This research uses an estuarine-watershed hydrodynamic–biogeochemical modeling system along with projected mid-21st-century changes in temperature, freshwater flow, and sea level rise to explore the impact climate change may have on future Chesapeake Bay dissolved-oxygen (DO) concentrations and the potential success of nutrient reductions in attaining mandated estuarine water quality improvements. [...]"

Source: Biogeosciences
Authors: Isaac D. Irby et al.
DOI: 10.5194/bg-15-2649-2018

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Oxygen Optode Sensors: Principle, Characterization, Calibration, and Application in the Ocean

Abtract.

"Recently, measurements of oxygen concentration in the ocean—one of the most classical parameters in chemical oceanography—are experiencing a revival. This is not surprising, given the key role of oxygen for assessing the status of the marine carbon cycle and feeling the pulse of the biological pump. The revival, however, has to a large extent been driven by the availability of robust optical oxygen sensors and their painstakingly thorough characterization. For autonomous observations, oxygen optodes are the sensors of choice: They are used abundantly on Biogeochemical-Argo floats, gliders and other autonomous oceanographic observation platforms.  [...]"

Source: Frontiers in Marine Science
Authors: Henry C. Bittig et al.
DOI: 10.3389/fmars.2017.00429

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The effect of bio-irrigation by the polychaete Lanice conchilega on active denitrifiers: Distribution, diversity and composition of nosZ gene

Abstract.

"The presence of large densities of the piston-pumping polychaete Lanice conchilega can have important consequences for the functioning of marine sediments. It is considered both an allogenic and an autogenic ecosystem engineer, affecting spatial and temporal biogeochemical gradients (oxygen concentrations, oxygen penetration depth and nutrient concentrations) and physical properties (grain size) of marine sediments, which could affect functional properties of sediment-inhabiting microbial communities. [...]"

Source: PLOS
Authors: Maryam Yazdani Foshtomi et al.
DOI: 10.1371/journal.pone.0192391

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Response of O2 and pH to ENSO in the California Current System in a high-resolution global climate model

Abstract.

"Coastal upwelling systems, such as the California Current System (CalCS), naturally experience a wide range of O2 concentrations and pH values due to the seasonality of upwelling. Nonetheless, changes in the El Niño–Southern Oscillation (ENSO) have been shown to measurably affect the biogeochemical and physical properties of coastal upwelling regions. In this study, we use a novel, high-resolution global climate model (GFDL-ESM2.6) to investigate the influence of warm and cold ENSO events on variations in the O2 concentration and the pH of the CalCS coastal waters. [...]"

Source: Ocean Science
Authors:  Giuliana Turi et al.
DOI: 10.5194/os-14-69-2018

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